I don't get it. Why does it have to be an ordered list?

If I write

```
2. Two
3. Three
5. Five
7. Seven
```

It should translate to that and not <small>(if you look [at the raw here][1] (or in pencil / show history button up there), you'll see I wrote just same thing)</small>:

2. Two
3. Three
5. Five
7. Seven

Where this weird standard conversion came from, and why does it persist for so long?

Even [that doc][2] @zzzzBov pointed does state:

> If you do use lazy list numbering, however, you should still start the list with the number 1. At some point in the future, Markdown may support starting ordered lists at an arbitrary number. 


  [1]: http://talk.commonmark.org/raw/1068/5
  [2]: http://daringfireball.net/projects/markdown/syntax#list